Solvent refining of hydrocarbon oil



ug. 16, 1938. L. A. CLARKE SOLVENT REFINING' OF HYDROCARBON OIL Filedoct. 2, 193s llulll NOU mOkmdamw mmJPPmw Dall LOUIS A. CLARKE lyNvENToRlll Patented aug. 1e, 193s UNITED sTATEs. AParam ori-lcs Louis A.Cnrksrisnkm, N. Y..Y signor to 'rhe Texas Company, New York, NrY., a.corpora- A\ tion of Delaware Application October 2 l 2 Claims.

This invention relates to a process lor solvent refining oi.'hydrocarbon oil, and more particularly for rening petroleum andiractions derived therefrom.

l The invention contemplates illus oil with a selective solvent of theamine type, such asv aniline, toluidine, etc. lt contemplates a methodin `which the amine solvent is recovered trom the oil subsequent to therednina operation by treatinc the mixture oi oil and amine with carbondioxide under conditions of temperature and pressure such that the neand carbon dioxide form an addition compound `which is substantiallyimmiscible with the oil so (that the coinpound can thus be readilyseparated trom the .1, oil by decantation or other means. lin thistorni, the amine is separated from the-oil and is subsequently recoveredlor reuse 'upon decomposition oi the addition compound.

It has been discovered that .amine compounds, such as aniline,toluidine, xylidene, etc., when mixed with. liquid carbon dioxide, insubstantially equal molecular proportions, torni compounds which arestable under pressure and which decompose with reversion to the originalcompounds when the pressure is' released. For example, it has been foundthat aniline and carbon dioxide, While under a pressure ci dllatmospheres, combine in. equal molecular proportions to form a compoundwhich crystallises at about dt lt. torming transparent white needles.lit a temperature of about 50 lil., the compound is in liquid form..When the pressure is released, the coinpound deccmposes into theoriginal compounds, aniline and carbon dioxide. The addition coinpoundis not formed in the presence ci Water under the above conditions, andtherefore dry or anhydrous carbon dioxide is employed.

ln effecting the formation ci. this addition coinpound, when usingcarbon dioxide, it is contem.-

plated employing temperatures oi around 50 to il6 F. 'and pressures inthe rance about 66d to i067 pounds per square inch aange.

lt is also contemplated that other acidic eases besides carbon dioxidemay be used, as for example sulphur dioxide and hydrogen sulphide.

Accordingly, my invention involves the application of the aboveprinciple tothe solvent renning of hydrocarbon oil, such as mineraloils,

as a means of recovering selective solvents oi tbe amine-type from theoil undergoing treatment.

This method of recovery is advantageously ap plied where the oilundergoing treatment is a gasoline fraction, and in which case theboiling point of the solvent is within the boiling range 1936, SerialNo. 103,660

(til. litt-i3) of the gasoline traction undergoing treatment,

so that it is impossible to separate the solvent from the pasoline bythe conventional distillation methods.

ln practicing the invention, the oil to be treated, which may beaasoline, naphtha, or a lubrieating oil traction ol petroleum, is minedwith a selective solvent ot the amine type, such as aniline. The mixtureof aniline and oil is separated into extract and ramnate phases. Theextract phase comprises the bulls: ol the solvent with the solubleconstituents oi the oil dissolved therein. The rnate phase comprises theinsoluble portion of the oil together `with a rela-- tively small amountoi the solvent liquid.

Thus, in the usual solvent reiinina operation, the extract phasecomprises the so-cailed nephthenic constituents dissolved inthe solvent,while the ramnate phase comprises the so-called paramnic constituents oithe oil mined with a sniall amount ci the solvent. l

"these two phases are separated and, in accordance with the method ot myinvention, are separately treated tvlth liquid carbon dioxide under theproper conditions ol temperature and. pressure. uThe aniline combineswith the carbon dioxide' to torni a compound, as already ex" plained,which, it the teinperatrue is su'mciently lovf, will be in crystallinelortu; or, at a slightly higher temperature, will be in a liuuid lortu.lihen it is in solid iorin, the crystals will, upon standina, separate,leaving the oilsubstantially free from the solvent and in a. conditionsuch that it may be Withdrawn by decantation.

On the other hand, where intermediate compound is in a liquid state, itsseparation from the oil may be effected by permitting the pointure tosettle and separate into layers. The hydrocarbon layer is removed as auupper layer, abile the solvent compound is withdrawn as a bottom layer.

ln order to illustrate the application oi my invention to the solventrednine` ol mineral oil, reference will now be made to theaccompanyine,l flow diagram.

The oil to be treated is withdrawn from a source not shown andintroduced to the lower portion oi an extraction tower l, while thesolvent, aniline, is also conductedl from a source not shown andintroduced to the upper portion of the extraction tower in theproportion of about one to three parts aniline to about one part oil.This extraction tower is advantageously of the conventional packed type,adapted to eiect countercurrent contact between the oil and the solvent.

lill

'I'he raiiinate phase accumulates in the upper portion of the tower,while the extract phase accumulates in the lower portion thereof.

The raffinate phase is continuously removed and conducted by a pump 2through a cooling coil 8 and a mixing coil l. It may not be necessary tosubject the raiiinate to cooling, depending, of course, upon thertemperature at which the extraction is carried out in the extractiontower I. If the extraction is made at a temperature oi' around 30 F..the railinate phase may not require any further cooling.

'I'he extraction temperature, in turn, depends upon the degree ofextraction desired as Well as upon the nature of the stock undergoingtreatment. For example. when extracting gasoline, the temperature mayrange from 32 to 100 F., while in the case of a lubricating oil stockthe temperature may range from to 210 F.

Liquid carbon dioxide is conducted from a tank 5 and commingled with therainate phase prior to its introduction to the mixing coil 4. Completemixing is effected within the coil I under superatmospheric pressureimposed upon the mixture by the pump 2. The carbon dioxide is mixed withthe railinate phase in equal molecular proportions with the anilinecontained in the rafilnate phase.

The mixture is conducted from the mixing oil 4 to a settling tank 6. Ifdesired, all or a portion thereof may be by-passed through a coil Ilocated within a separator 8 to which reference will be made later. Themixture of carbon dioxide and ramnate phase is allowed to settle in thesettling tank 6, while still maintained under superatmospheric pressuresufficient to cause the aniline and the carbon dioxide to combine toform ythe addition compound. Separation into phases occurs within thetank 6, and the raffinate oil, substantially free from the solvent, iswithdrawn from the upper portion thereof as indicated.

The addition compound formed by the aniline and the carbon dioxide iswithdrawn from the bottom of the tank 6 and conducted to the separator8, previously referred to. 'Ihe pressure within the separator 8 isreleased so 'that the carbon dioxide vaporizes and decomposition of thereaction compound occurs. The vaporization of the carbon dioxide resultsin a refrigerating effect, and this is utilized to cool the mixture ofcarbon dioxide and rafllnate phase passing through the coil l within theseparator 8. As a result of the reduction in pressure, the additioncompound is decomposed into aniline and carbon 1 dioxide. The carbondioxide is withdrawn, as

indicated, and is then conducted to a compressor not shown, wherein itis liquefied and returned to the storage tank 5.

The separated aniline is withdrawn from the bottom ofthe separator 8,and is available for mixing with fresh oil in the extraction tower I.

In a similar manner, the extract phase is conaumen tinuously withdrawnfrom the bottom of the extraction tower I through a cooling coil I andfrom there through a mixing coil III.

As already indicated, in connection with the raffinate phase, thecooling of the extract phase may be omitted.

Carbon dioxide in the proper proportion is mixed with the extract phaseprior to its passage through the mixing coil I0, and from there themixture is conducted to a settling tank I I, similar to the settlingtank 6. Also, the mixture of ani- 1 line and carbon dioxide may beby-passed, all or in part, through a cooling coil I2, located within theseparator I3, similar to the separator 8.

The mixture within the settling tank II, and under superatmosphericpressure, separates into phases or layers. 'I'he oil layer comprising anextract oil is removed from the upper portion thereof. while theaddition compound of aniline and carbon dioxide is removed from thelower portion of the settling tank to the separator I3, already referredto. A

'Ihe pressure is released within the separator I3 so that the compounddecomposes into its components, carbon dioxide and aniline, which areremoved therefrom for reuse in a manner similar to that described inconnection with the recovery of this compound from the raffinate phase.

Obviously, many modifications and variations of the invention, ashereinbefore set forth, may be made without departing from the spiritand scope thereof, and therefore only such limitations should be imposedas are indicated in the appended claims.

I claim:

1. In the refining of hydrocarbon oil by solvent extraction with anamine type of extraction solvent at a temperature above about 50 F., themethod of recovering the amine from the oil comprising mixing the oilcontaining the amine with anhydrous carbon dioxide under a pressuresubstantially elevated above atmospheric such that the amine and carbondioxide combine forming an addition compound which is substantiallyimmiscible with the oil and which decomposes upon reduction of pressureto atmospheric without application of heat, passing the mixture to asettling zone maintained under said elevated pressure, withdrawingtherefrom Vthe* addition compound, introducing the withdrawn compound toa zone of reduced pressure to decompose into carbon dioxide and theoriginal amine, and refrigeratively vaporizing the carbon dioxidetherefrom while in indirect thermal contact with the mixture beingcharged to said settling zone, thereby cooling the mixture to atemperature of 50 F. and below.

2. The method according to claim 1 in which the amine comprises aniline.

LOUIS A. CLARKE.

